Overcenter backhoe



June 25, 1968 E. 5. LONG 3,389,816

OVERCENTER BACKHOE Filed Oct. 28, 1966 5 Sheets-Sheet l rroelve VS June 25, 1968 E. B. LONG OVERCENTER BACKHOE Filed Oct. 28, 1966 June 25, 1968 E. B. LONG OVERCENTER BACKHOE 5 Sheets-Sheet 3 Filed Oct. 28, 1966 /Nl NTOB 56 3-46??? United States Patent 3,389,816 OVERCENTER BACKHOE Elton B. Long, Burlington, Iowa, assignor to J. I. Case Company, a corporation of Wisconsin Filed Oct. 28, 1966, Ser. No. 590,367 Claims. (Cl. 214-138) ABSTRACT OF THE DISCLOSURE A backhoe arrangement is disclosed to accommodate overcenter movement of the dipper so that the dipper may swing either upwardly or downwardly of an extended central or neutral position relative to the boom, such position being defined when a straight-line relationship exists between the line of action of the dipper cylinder and the pivot point between the boom and dipper. The dipper cylinder is positioned upwardly of neutral position for conventional ditch or trench digging and is positioned downwardly of center for undercut digging operations. When the dipper cylinder is downwardly of center, the backhoe mechanism can be swung to a transport position wherein the dipper overlies the tractor so that the center of gravity of the backhoe mechanism is more forwardly located and establishes a better weight ratio on the tractor wheels.

This invention relates to power-driven shovels and, more particularly, is concerned with a backhoe mechanism mounted on a tractor or similar vehicle and suited to versatile digging and also to convenient transport.

In the conventional prior art backhoe arrangements, the machines are normally equipped only for digging ditches, or for digging deep trenches, as the arrangement only accommodates single-sided movement of the dipper with respect to the boom. In such prior art arrangements, the transport position is characterized by a generally vertically extending boom with the dipper pulled in as close as possible to the boom to hold the main center of gravity for the backhoe as near as possible to the rear of the mounting vehicle. However, the main center of gravity is still so far to the rear of the vehicle that mechanical balance relationships are insufficiently stable, this being particularly noticeable when the vehicle is moving in high-speed trafiic.

In accordance wtih the present invention, a backhoe arrangement is provided to accommodate an overcenter dipper movement in that the dipper may swing in both directions, or to both sides of its extended positions relative to the boom. The backhoe arrangement has an articulated dipper cylinder mounting arrangement for which a central or neutral position is defined when a straight-line relationship exists between the line of action of the dipper cylinder and the pivot point between the boom and dipper. The mechanism is arranged so this relationship exists when the dipper is substantially extended and, in this extended centerline position, the parts may be readily actuated to either side of center. The present backhoe mechanism has the dipper cylinder pivotally articulated to the boom to be selectively oriented either upwardly or downwardly of center. When digging ditches or deep trenches, the boom and dipper are operated in the conventional fashion wherein the dipper cylinder is upwardly of center.

Finally the ability of the dipper cylinder to assume a downwardly of center relation to the boom enables the dipper to be swung to a transport position, where it overlies the top of the vehicle, resulting in the center of gravity of the entire backhoe mechanism being established substantially forwardly of the position obtained in the prior art arrangements thereby establishing a better weight ratio on the wheels through a more advantageous position of the dipper mass.

An important advantage of the overcenter backhoe arrangement of this invention is its adaptability to undercut digging. Such undercut operations are frequently required in excavating under sidewalks and streets where minimum break-through is desired in the concrete. Undercut digging is accomplished by configuring the parts so that the dipper cylinder is oriented in a downwardly of center relationship, with the dipper leading laterally from the lower extremity of the boom and carrying the bucket in an extended inverted position. The downward incline of the boom in this arrangement is dependent upon the depth of the undercut region being excavated.

Other features and advantages of the invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which show structure embodying preferred features of the present invention and the principles thereof, and what is now considered to be the best mode in which to apply these principles.

In the accompanying drawings forming a part of the specification, and in which like numerals are employed to designate like parts throughout the same:

FIGURE 1 is a sectional and a side elevational view of one embodiment of a backhoe mechanism in accordance with this invention illustrating the same in minimum transport position;

FIGURES 1A, 1B and 1C are fragmentary views of a stop pin assembly;

FIGURE 2 is a related side view of the backhoe of FIG. 1 illustrating the normal position assumed at the completion of a ditch-digging stroke;

FIGURE 3 is a related side view of the backhoe illustrating the same in normal digging position slightly upwardly of center;

FIGURE 4 is a related side view of the backhoe illustrating the same in substantially neutral or centered position;

FIGURE 5 is a related side view illustrating the backhoe in the midst of an undercut digging operation; and

FIGURE 6 is a related side view picturing the backhoe in maximum transport position.

Referring now to the drawings, a backhoe arrangement designated generally at 10 is shown mounted upon the rear of a tractor, which is illustrated fragmentally as indicated at T. The backhoe includes a mounting bracket B which may be attached to rotate about a vertical axis. The mounting bracket, in the embodiment illustrated in FIGURES 1 to 6, has a boom cylinder 11 pivotally mounted at the top and a boom 12 pivotally mounted at the bottom, and each rotatable about a horizontal axis. The boom cylinder 11 is of a double-acting type and has a single-ended piston rod 13 pivotally connected to a top marginal corner 12T of the boom. Thus, the boom is swingable in a conventional way from a vertical orientation, pictured in FIGURES 1 and 6-, to horizontal orientations, pictured in FIGURES 2, 3, and 4, and finally to a downwardly inclined orientation, pictured in FIGURE 5.

In the illustrated arrangement, the boom is of a twinbeam construction and a single boom cylinder is centered above the beam. Alternatively, a separate boom cylinder may be provided extending along the top edge of each boom.

A pivot shaft 14 is carried at a bottom edge corner of the boom and mounts a dipper 15 for pivotal swinging movement from the boom 12. The dipper pivot shaft 14 defines a pivot axis for the dipper at a location intermediate along its length, but substantially closer to its boom end than to its bucket end. The boom end of the dipper 15 terminates in a generally triangular attachment plate portion 15P which carries the pivot shaft 14. A single-dipper cylinder 16, which is also double acting 3 1 and includes a single-ended piston rod 17, is disposed within the twin beam structure of the boom. The dipper cylinder 16 is articulated tothe boom to swing about a pivot shaft 18 carried by the boom. The dipper cylinder piston rod 17 is pivoted to the adjacent end of the dipper attachment plate by means of a pivot shaft 19.

A bucket 20 is pivoted to the free end of the dipper in the usual way and is'controlled by a pair of drive links 21 and 22, respectively, link 21 being pivoted to the dipper and link 22 to the bucket. Finally, the links 21 and 22 are interconnected by a floating knee shaft 23. A double acting bucket cylinder 24 is pivot-ally mounted to a shaft 25 carried on the dipper attachment plate 15F and extends along the dipper. The cylinder 24 is also of the double acting type having a single-ended piston rod 26 'drivingly connected to the knee shaft 23. Y

Unique relationships exist in the mechanical linkage between the boom cylinder 11, the boom 12, the dipper 15 and the dipper cylinder 16 to provide a neutral or center position for the backhoe mechanism and to enable the backhoeamechanism to be actuated to either side of this center position. A knee joint is defined by the shaft 14 between the boom 12 and the dipper 15. The dipper and boom and the knee joint are substantially extended at the center position which corresponds to full retraction of the cylinder 16 and piston rod 17. A reference plane defined between the pivot shaft 18 for the dipper cylinder and the dipper pivot shaft 14 represents the neutral or center line position for the dipper'cylinder 16 (see FIG.

.4). When the line of action of the dipper cylinder 16 is above this plane, as is true in FIGURES 1, 2 and 3, the backhoe mechanism is referred to as being upwardly of center and the knee is flexed in one direction and when the line of action of the dipper cylinder 16 is below this reference plane, as is true in FIGURES 5 and 6, the backhoe mechanism is here referred to as being downwardly of center and the knee is flexed in an opposite direction. The versatile application of the present backhoe will now be described with reference to its various conditions of use and its final position of storage for transport.

Beginning with FIGURE 6, the backhoe is shown in its maximum transport position wherein theboom cylinder piston rod 13 is retracted and the dipper cylinder piston rod 17 is extended. To move from the maximum transport position of FIGURE 6 to the minimumtransport position of FIGURE 1, the dipper cylinder 16 is actuated to retract the piston rod 17 until the dipper is substantially fully extended and the dipper cylinder is substantially aligned in the reference plane. At this point, the weight of the dipper bucket acts to carry the parts over center when the control valve for the dipper cylinder is reversed. The backhoe is then in its minimum transport position as illustrated in FIGURE 1 and is ready for normal digging of ditches or deep trenches, this being illustrated in FIGURE 2.

When it is desired to perform undercut digging, the backhoe is first brought from its normal digging position to the transitional position of FIGURE 3 and finally to the neutral or center position of FIGURE 4. This is accompli'shed by lowering the boom while retracting the dipper cylinder piston rod until the neutral position of FIGURE 4 is achieved.

To move downwardly of center, the boom cylinder piston rod 13 is extended to react the bucket 20 against the ground while the dipper cylinder piston rod 17 is allowed to extend. Continued movement in this direction under the action of the control valve will bring the parts of the undercut digging position of FIGURE 5.

When the backhoe is in a downwardly of center relationship, theparts may also be swung to the maximum transport position of FIGURE 6 by concurrently raising the boom and extending the dipper cylinder piston rod 17. There is an important advantage in the particular configuration of the backhoe in its maximum transport position. The center of gravity of the backhoe establishes a 4 more-balancedweight ratio on the tractor wheels by reason of the forward position at which the dipper mass acts.

The ability of the articulated dipper cylinder to be controlled to the neutral or center position by the action of the usual control valve (not shown) enables the backhoe mechanism to be selectively-positioned to either side of center. This gives greater versatility while maintaining overall simplicity in the arrangement. Q

A number of modifications to the arrangement are contemplated. The boom may be pivoted to the top of the bracket B and the boom cylinder may extend beneath the boom to extend for raising the boom and. to retract for lowering the boom. In lieu of a twin beam boom, a single centered beam flanked by a pair 'of pivotally mounted dippercylinders may be used. Still anothef'alternative contemplates an offset arrangement wherein a dipper is offset'from a single beam type of boom and is operated by a dipper cylinder that extends -'al'ongside'the boom and in general alignment with the dipper. 3

A positive stop 27 is provided along the dipper to engage the knee end of the boom for determining the configuration of the parts in the maximum transport position. Since in normal operation, the backhoe is maintained in either an upwardly or downwardly of center relation while performing a particular digging operation and isnot intended to repeatedly reverse its configuration, a'selectively operable positive stop 28 may be provided to be rendered inoperative only when the backhoe is to be moved through its center position.

The stop pins 27, 28' may' be of identical form and, therefore, only pin 27-is shown in detail in FIGS. 1A, 1B and 10 wherein it is represented in the form of a click pin assembly. The pin 27 projects transversely through the dipper 15. An anchor collar 29 afiixed to the dipper 15 carries a retaining pin 30 for one end of a lock ring 31 that encircles the collar and normally locks the retaining pin 30 in place. The lock ring 31 may be swung free of the collar to enable removal of the retaining pin 30 which then enables axial shifting of pin 27.

It may be observed that stop pin 27 is only effective when the backhoe is in its maximum transport position. For all other positions and movements of the backhoe, the pin 27 is not active. The pin 28, however, must be retractable through its mounting hole in the boom 12 to enable the backhoe to move from one side of center to the other.

Thus, while preferred constructional features of the .invention are embodied in the structure illustrated herein, it is to be understood that changes and variations may be made by those skilled in the art without departing from the spirit and scope of the appended claims.

What is claimed is:

1. In a backhoe arrangement that includes a boom mounted to swing about a first horizontal axis, adipper, first horizontal pivot means engaging said boom at a point adjacent a free end thereof and engaging said dipper at an intermediate portion to define a horizontal knee axis for relative vertical swinging movement between said boom and dipper, dipper cylinder and piston mechanism disposed alongside said boom, second horizontal pivot means mounting one end of said mechanism on the boom at a point remote from the knee axis, and third horizontal pivot means mounting the other end of said mechanism at apoint on the dipperadjacent the extremity of the knee end thereof, the improvement wherein said boom and said dipper have vertical clearance between lengthwise overlapping portions thereof -whereby' the knee end portion of said dipper is freely vertically swingable relative to said boom to assume an extended neutral position and to assume positions on either side thereof, and wherein said mechanism is freely vertically swingable relative to said boom and to said dipper and said mechanism is retractable to alength to locate said first, second and third pivot means in alignment and to locate said dipper said extended neutral position selectively to enable extension of said mechanism to etfect swinging of siad dipper to either side of said neutral position.

2. In a backhoe arrangement in accordance with claim 1 and wherein said mechanism has a dipper cylinder mounted to said second pivot means and a dipper piston rod mounted to said third pivot means.

3. In a backhoe arrangement in accordance with claim 1 and including a mounting bracket having said boom pivoted to a lower corner portion to define said first horizontal axis and having one end of said boom cylinder and piston means pivoted to an upper corner portion thereof and extending above said boom, said boom terminating in an enlarged knee end having a bottom corner portion mounting said first pivot means and having a top corner portion mounting said second pivot means.

4. In a backhoe arrangement in accordance with claim 2 and including a mountnig bracket having said boom pivoted to a lower corner portion to define said first horizontal axis and having one end of said boom cylinder and piston means pivoted to an upper corner portion thereof and extending above said boom, said boom terminating in an enlarged knee end having a bottom corner portion 'mounting said first pivot means and having a top corner portion mounting said second pivot means.

5. In a backhoe arrangement that includes a boom mounted to swing about a first horizontal axis, boom cylinder and piston mechanism connected to swing said boom about said first axis, a dipper, first horizontal pivot means engaging said boom at a point adjacent free end thereof and engaging said dipper at an intermediate portion to define a horizontal knee axis for relative vertical swinging movement between said boom and dipper, and means mounting a dipper cylinder and piston mechanism along said boom, the improvement wherein said boom and said dipper have vertical clearance between lengthwise overlapping portions thereof whereby the knee end portion of said dipper is freely vertically swing-able relative to said boom to assume an extended neutral position and to assume positions on either side thereof, and wherein said dipper cylinder and piston mechanism includes horizontal pivot 'rneans drivingly connecting said dipper cylinder and piston mechanism to act at a point on the dipper adjacent the extremity of the knee end thereof, and, when in retracted position, locates said dipper in said extended neutral position selectively to enable extension of said dipper cylinder and piston mechanism to efi'ect swinging of said dipper to either side of said neutral position.

References Cited UNITED STATES PATENTS 3,042,233 7/1962 Wills 2l4138 3,220,578 11/1965 Pilch 214-138 HUGO O. SOHULZ, Primary Examiner. 

